1. Field of the Invention
The present invention is directed to a method of making nanosized copper (I) compounds and the resultant nanosized copper (I) compounds. In particular, the present invention is directed to a method of making nanosized copper (I) chloride, copper (I) cyanide, and cyanocuprate complexes.
2. Description of Related Art
Nanometer sized particles have diameters in the range from about 1 nanometer (10−9 meter) to about 100 nanometers (10−7 meter). These materials are also described in the art as nanostructured, nanocrystalline, nanosized, nanoparticulate, nanoscale, ultrafine, or superfine. Their structures and high surface to volume ratio make them desirable in catalytic, electronic, magnetic, and coating (pigment) applications. Various physical and chemical methods have been disclosed in the art for their preparation.
Nanosized copper (I) chloride is desired for its nonlinear optical properties and its utility in optoelectronics. There is a need for nanosized CuCl to satisfy the many laser and other applications in this field. The known art (see T. Ito, Seramikkusu, 27:508-514 (1992); A. Onushchenko, et al., J. Non-Crystalline Solids, 196:73-78 (1996); T. Ito et al., in Mesoscopic Materials and Clusters (T. Arai, Editor), Springer, Berlin, (1999), pp, 31-46, discloses synthesis of nanosized CuCl embedded in glass, alkali halide, and polymer matrices. However, the synthetic methods used are not suited to catalytic applications or to the isolation and recovery of nanocrystalline CuCl.
Copper (I) cyanide, CuCN, is a copper source for yttrium-barium-copper oxide superconductors, copper plating baths, and as a catalyst for Grignard and other alkylation reactions. Solid cyanocuprates such as M[Cu(CN)2], M[Cu2(CN)3], M2[Cu(CN)3] and M3[Cu(CN)4] where M is sodium, potassium, or other metal, are important in the recovery of copper from ores. They have infinite microporous frameworks, which have utility in molecular sieves and catalysis.
It is known in the art to dissolve a soluble copper (II) compound in the polar phase of a reverse micelle/microemulsion of defined polar phase to surfactant molar ratio. A reducing agent (for example, NaBH4 or N2H4) is dissolved in the polar phase of another sample of the same reverse micelle/microemulsion. Mixing the two samples leads to reduction of Cu (II) and formation of nanosized copper (I) oxide and/or nanosized copper metal. Cu2O with 5-10 nanometer particles was prepared in this way by Zou, et al. (Chinese Science Bulletin, 39:14-18(1994)). Lisecki, et al. (J. Physical Chemistry, 100:4160-4166 (1996)) disclosed the control of copper particle size and dispersity by control of water/surfactant molar ratio. Nanoparticles 2-10 nanometers were obtained at molar ratios, 1-10. Qi, et al. (J. Colloid and Interface Science, 186:498-500 (1997)) also prepared 5-15 nanometer copper particles in reverse micelles. M. P. Pileni (J. Physical Chemistry, 97:6961-6973(1993)) has reviewed the subject. In general, use of sodium borohydride or hydrazine does not allow careful, selective reduction to a nanosized copper (I) product from the copper (II) precursor, but rather complete reduction to nanosized copper (0) metal.
U.S. Pat. No. 5,770,172 to Linehan et al. issued on Jun. 23, 1998, discloses a process for producing nanometer-sized metal compounds comprising forming a reverse micelle or reverse microemulsion system comprising a polar fluid in a non-polar or low-polarity fluid. Again, as in the references cited above, the types of reducing agents used, i.e., phosphates, hydrazines, sodium borohydride, do not allow selective reduction to the copper (I) product from the copper (II) precursor. The reduction proceeds to the elemental metal.
Although it is known that the reduction of CuCl2 to CuCl can be effected by ascorbic acid (E. Stathis, Chemistry & Industry (London), 1958, p 633), by sulfites and reducing sugars (G. Fowles, The School Science Review, 44(1963) pp 692-694), and by phosphorous acid (R. N. Keller, Inorganic Syntheses, Vol. II, 1946, pp 1-4), there are no known previous applications of these chemistries to the synthesis of nanosized CuCl.
U.S. patent application Ser. No. 09/974,503 filed Oct. 9, 2001 teaches the preparation of nanosized CuCl by reaction of nanosized Cu2O with HCl in hydrocarbon solvents, or in a gas-solid environment. Reduction of Cu(II) is not essential since the nanosized Cu2O can be formed by any physical or chemical method available.
Notwithstanding the state of the prior art, it would be desirable to provide a method of making nanosized copper (I) compounds wherein there is a controlled and selective reduction from the copper (II) precursor to the copper (I) product and the resultant nanosized copper (I) compounds.